How to prevent Brute force attacks in Debian systems without fail2ban or CSF-LFD?
The closest and fastest way I know is ConfigServer's
CSF-LFD but it's not in the repositories and if I'm going to use a utility I would most prefer something in the repositories (it seems I cannot create a Debian/Ubuntu repository for it because of licensing/legal reasons).
Another solution than CSF-LFD is
Fail2ban but it seems to me that the Fail2ban configuration requires firm knowledge in IPS software architecture as well as deep knowledge of Perl compatible regex (PCRE), which both I currently lack (I have some basic PCRE knowledge but not as deep as I think one needs for Fail2ban). It doesn't seem straight forward as CSF-LFD to me.
Thus I wonder if there is a "smoother" way, maybe manually via IP tables, maybe via some utility I could install directly from the Debian/Ubuntu repositories that could prevent BFAs besides the issue of using SSH keys.